v3.26.3
Investments - Amortized Cost and Fair Values of Investment in Fixed Maturities (Details) - USD ($)
$ in Millions
Sep. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost $ 733.7 $ 706.0
Gross Unrealized Gains 0.0 2.8
Gross Unrealized Losses (12.8) 0.0
Fair Value 720.9 708.8
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 466.3 499.2
Gross Unrealized Gains 0.0 2.0
Gross Unrealized Losses (9.2) 0.0
Fair Value 457.1 501.2
U.S. Government obligations    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 158.0 139.5
Gross Unrealized Gains 0.0 0.6
Gross Unrealized Losses (2.9) 0.0
Fair Value 155.1 140.1
Asset-backed securities and collateralized loan obligations    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 80.3 45.3
Gross Unrealized Gains 0.0 0.2
Gross Unrealized Losses (0.5) 0.0
Fair Value 79.8 45.5
Non-U.S. government obligations    
Debt Securities, Available-for-sale [Line Items]    
Cost or Amortized Cost 29.1 22.0
Gross Unrealized Gains 0.0 0.0
Gross Unrealized Losses (0.2) 0.0
Fair Value $ 28.9 $ 22.0